Specific Latent Heat

A substance loses thermal energy (heat) to the surroundings at a steady rate. The graph shows how the temperature of the substance changes with time.

What could the portion PQ of the graph represent?

• gas condensing

• gas cooling

• liquid cooling

• liquid solidifying

A mass of 0.20 kg of a substance is initially solid.

It is heated at a steady rate of 500 W.

The graph shows how the temperature of the substance changes with time.

What is the specific latent heat of fusion of the substance?

• 20 000 J/kg

• 30 000 J/kg

• 500 000 J/kg

• 7500 000 J/kg

In an experiment, a liquid is heated at a constant rate.

The temperature of the liquid increases and eventually becomes constant.

Which statement about the experiment is correct?

• Boiling occurs at all temperatures but only on the liquid surface.

• Boiling occurs throughout the liquid but only at the constant temperature.

• Evaporation occurs throughout the liquid and at all temperatures.

• Evaporation occurs only at the constant temperature and only on the liquid surface.

5.0g of water at 25°C is dropped onto a large block of ice at 0°C. The water cools to 0°C and some of the ice melts.

Assume that all the energy lost by the water is gained by the ice.

What is the mass of ice that melts?

The specific heat capacity of water is 4.2 J/(g°C).

The specific latent heat of fusion of ice is 340 J/g.

• 0.062 g

• 0.087 g

• 1.5 g

• 10 g

A liquid is at a temperature below its boiling point.

The liquid is then heated so that it becomes a gas at a temperature above its boiling point.

Which row correctly compares the liquid with the gas?A

• A

• B

• C

• D

Which statement describes what happens as ice at 0°C starts to melt to become water?

• Energy is absorbed and the temperature remains constant.

• Energy is absorbed and the temperature rises.

• Energy is released and the temperature remains constant.

• Energy is released and the temperature rises.

Equal masses of two different liquids are heated using the same heater. The graph shows how the temperature of each liquid changes with time. What does the graph tell us about the liquids?

• Liquid 1 has a higher melting point than liquid 2.

• Liquid 1 has a higher boiling point than liquid 2.

• Liquid 1 starts to melt sooner than liquid 2.

• Liquid 1 starts to boil sooner than liquid 2.

In an experiment, a thermometer is placed in a test-tube of hot liquid. The temperature of the liquid is recorded every half minute. The table shows the results. What is the melting point of the substance?

• 0°C

• 33°C

• 55°C

• 73°C

When steam condenses it becomes liquid water. When liquid water solidifies it becomes ice.

What happens to the temperature of steam while it is condensing, and what happens to the temperature of water while it is solidifying?

• A

• B

• C

• D

A solid is heated from room temperature. The graph shows how its temperature changes with time as it is heated constantly. Between which labelled points on the graph is the substance partly solid and partly liquid?

• between P and Q

• between Q and R

• between R and S

• between S and T